At present, most users are using traditional telephone system as their communicating method. Traditional telephone system comprises PBX, phone and telephone wire. Users are to pay for their calling to the communication operator. Especially for enterprises, it will increase their cost.
Because of the development of VOIP technology, network telephone system is accepted and applied by many enterprises due to its lower cost than traditional telephone system. However the software telephone system exists with its limitations, take Skype (a software of network telephone used widely) for example, it is available only for software telephone to call landline phone (or mobile phone), and the call between software telephones. For the call between software telephones, it might be free of charge because the voice data packet is transmitted by internet; and for the call from software telephone to landline phone (or mobile phone), the network telephone operator will pay the traditional telephone operator because they exist separately, thus the users are to pay (for example: skype recharge) the network telephone operator; it is not available for Skype to achieve the call from landline phone to software telephone and the call between landline phones.
With the developing of network technology, new solutions are being arisen constantly, for example, Cisco-voip shown in FIG. 1, the hardware devices comprise: router, switch, PBX, PC, phone, network cable and telephone wire. PC connected to PBX through network cable, PBX connected to router through network cable, router with its speech interface connected to PBX through telephone wire, and phone connected to PBX through telephone wire. Execution program: for example, company A calls company B. The administrator of company A customizes a prefix number, when company A staff firstly dials the prefix number before dialing phone call, PBX will transmit the voice data packet to the router of company A, and the router of company A will find through addressing the router of company B which has been set in advance (transmission process for calling data is shown as FIG. 2 Cisco-voip process). There is no soft end in this solution, so it is unavailable to achieve the cross dialing between software telephone and landline phone, and between software telephones. It is only available for the cross dialing between landline phones to be free of charge, because the prefix number is customized by enterprise network administrator, who must unify the planning of the routing information of company A and B in advance before cross dialing, thus the routers outside of the unified planning could not exchange with them. In a word, the prerequisite of this solution is that the two companies must be headquarters and branch, and the PBX in this solution must be high end with specific voice interface. Because of the high cost, it is not suitable for most small and medium-sized enterprises.
With the developing of network hardware devices, there is a further development in traditional VOIP solution. Take IPT solution of Cisco for example, Cisco-IPT shown in FIG. 3, the hardware devices comprise: router, switch, call manager (phonological load, distribute extension number for IP telephone), IP telephone, PC and network cable. PC connected to IP telephone through network cable, IP telephone connected to switch through network cable, call manager connected to switch through network cable, and switch connected to router through network cable. For example, company A calls company B. Transmission process for calling data is shown as FIG. 4 Cisco-IPT process, when staff in company A calls staff in company B, he will firstly dial the prefix number (same as in Cisco-VOIP solution, also need the enterprise network administrator to customize in advance), the voice call data packet will be transmitted to the switch, then to call manager. After processing data, call manager will transmit it to the router of company A through switch, and the router of company A will find through addressing the router of company B. In this solution, call manager takes place of the traditional telephone switch, and the soft end phone is added. The prerequisite of this solution is that the planning of the routing information must be unified for company A and B in advance before cross dialing, thus the routers outside of the unified planning could not exchange with them. Which is to say, it will be free of charge in cross dialing only for the companies whose relations are the headquarter and branch. Meanwhile, Because of the high cost for call manager and IP telephone, it is difficult to afford by general small and medium-sized enterprises.